Smartphones can be used for almost everything. Fitness watches acquire health data. IT-equipped automobiles can drive themselves. Everyday objects are growing smarter and smaller, but what about the factories which manufacture products? Takahashi Laboratory, which focuses on advanced manufacturing using light, engages in research into extremely tiny factories which create devices so small they cannot be held. Let's learn more.

Professor Takahashi enjoys talking with students while performing an experiment

■ Using light as a tool to revolutionize manufacturing

“Modern factories use technology to create items that in some cases measure even less than 20nm, but in the end these are used to create products which are large enough to be held by people. Our vision is of factories which automatically manufacture components and devices so small they cannot be held by hand. These factories themselves would fit into boxes measuring just a few dozen millimeters. These would be completely unprecedented," explains Professor Takahashi.
Takahashi Laboratory explores the potential of optical technologies for measurement and processing, and aims to create tiny cell-in-micro-factories using light as their ultimate tools.

Professor Takahashi says that light is a tool. "Optical technology is a tool that can be used for measurement and processing. It is like a doctor's stethoscope, scalpel, and tweezers. One of the advantages is that light serves all of these functions.
The ‘cell-in-microfactory' concept combines the different optical techniques used in a lab."
Take, for example, measurement. When looking at objects with light, the maximum resolution is normally roughly 200nm, and an electron microscope is necessary to observe smaller details. While electron microscopes do offer high resolutions, they generally require vacuum environments, which is an impediment to their use in manufacturing sites. If the advantages of light, which is not limited to vacuum environments, were expanded, the quality of optical measurement could be improved, changing the face of manufacturing. Takahashi Laboratory is researching an "optical super resolution using localized light shift" which moves light and performs complex calculations to observed areas which cannot be observed through mere light exposure. The laboratory is also engaged in other research which can directly lead to manufacturing revolutions, such as the fabrication of three-dimensional structures using photocatalyst nanoparticles, which uses chemical reactions to produce microstructures, and autonomous defect detection probes (divided multiprobes), which use liquid to automatically detect defects on silicon wafers, such as contaminants.
"With advances in research into manufacturing using a special type of light called evanescent light we could produce 3D printers capable of working with extremely thin layers, on the order of 100nm. We may be the only people in the world researching stereolithography using evanescent light," says Professor Takahashi as he showed us the gingko image shown below.

A gingko tree leaf, the University of Tokyo's symbol, created using evanescent light.
It is a single manufactured piece, just 100nm thick, on a field measuring 100μmx100μm
(created by Mr.Suzuki of the Takahashi Laboratory)

■ Invisible "evanescent light" lights up the future

Vision is one of the most important senses because of the sheer amount of information it provides. Vision is made possible by light, which Professor Takahashi declares is a tool. The light that we normally see is either given off by objects, or reflected and scattered by objects, passing through space to reach us. In other words, the light we normally use is always propagated. Evanescent light, however, is the small amount of light that penetrates the material with the lower refractive index when light strikes materials with different refractive indices at a specific angle and undergoes total internal reflection, without losing any information. Takahashi Laboratory, focusing on the fact that this light is not propagated through space, and penetrates to a depth of only around 100nm, began researching techniques for applying evanescent light to stereolithography.
"Based on the fact that information is retained because the light is not propagated, and that the layer is extremely thin, our goal is to develop 3D printers with a printing layer thickness on the order of 100nm. Objects are made, not by scanning 'points', but by simultaneously printing 'areas', so this would make it possible to create special objects such as thin, flat panels with complex micro-functional structures," says Professor Takahashi.
If this technique were used in microprocessing the surfaces of photovoltaic panels, it could contribute to reducing the amount of light reflection and improving light collection rates. "Conventional devices have a single layer thickness of around 5μm. This is equivalent to fifty 100nm layers made using evanescent light. Evanescent light could be used for even higher precision manufacturing."
So far, the laboratory has succeeded at creating objects made up of ten layers, each several hundred nm thick. There are still challenges with lamination stability, but Professor Takahashi feels confident, saying "Evanescent light carries highly detailed information, so it was originally used for measurement. Because that energy is localized, it can, of course, also be used for processing. When the idea of stereolithography was first developed, it took an extremely long time just to harden resin using evanescent light. Honestly, at first I thought that we had reached the limits of what was possible, but my students worked hard, and we overcame that hurdle. We're now seeing all kinds of possibilities which at first we didn't even imagine. It's important to persevere in one's research (laughs)."

When we can see things which we have never been able to see before, and create things we have never been able to create before, cell-in-micro-factories will integrate these optical manufacturing technologies. These factories, smaller by far than anything that has come before, are Professor Takahashi's own original idea. The smallest factories which exist today are "desktop micro-factories," which consist of machine tools such as micro-lathes. Cell-in-micro-factories, measuring just several dozen millimeters wide by several millimeters deep, are to contain the most advanced optical technologies, performing everything from measurement, processing, and handling to conveyance and defect detection. The objects they manufacture will measure less than 1 millimeter. When asked where his creativity springs from, Professor Takahashi answers, "I come from Kansai, so I love comedy. Comedy consists of gaps, right? I think research works the same way. You need surprising gaps, where people think you're going to go one way, but then you come at them out of left field. I often send myself emails with ideas I think up in the morning, when I'm still kind of out of it."
Professor Takahashi continues, in Osaka dialect, "My research is application oriented, thinking about factories and manufacturing, but I also want to work with light. Light is a really fundamental energy. The reason why life arose on earth and why we have petroleum is the light provided by the sun long, long ago. We're all benefitting from that. There are a lot of aspects of light that science still needs to explore. What's interesting about our research is that we study light, but we also work on practical applications." Professor Takahashi talked enthusiastically about his research, but said lately there's been something that has worried him.
"In my lectures...my jokes always go over like lead balloons. There are just these dead silences."

"Cell-in-micro-factories", factories you can hold between your fingers
Micro-miniaturization leads to ultra energy saving. The future of manufacturing, overturning the conventional factory concept.

Researcher Profile

Professor Takahashi loves to travel. During university he spent two months circling Australia on motorcycle. Motorcycles can't carry a lot, but he needed to have supplies on hand in case of an accident. Managing this took some creativity. "Even now, I love packing luggage," says Professor Takahashi. Professor Takahashi's laboratory operating motto is "Always take on new challenges, being meticulous yet bold." His adventurous travels embody this approach: meticulous preparation and response and bold action. "It applies whether you're dealing with things or with people. Small structures are easily affected by surface tension. You need to imagine how these objects feel in order to do our research. You need to be considerate to work well as a team." Professor Takahashi describes the members of his laboratory, "They are really characters. We have a student who won the President's Prize, a student in the ballroom dancing club, and the leader of the cheer squad. One of the things that make working in a university research lab so interesting is the opportunity to meet new people with such diverse talents each year."